In a liquid crystal panel, a polarizing plate is used to control optical rotation of light beams that pass through liquid crystals. Conventionally, in such a polarizing plate, a polarizing plate obtained by dying a polymer film, such as a polyvinyl alcohol or the like with iodine or a dichromatic dye and stretching the film in one direction has been widely used. However, there has been a problem that the aforementioned polarizing plate is poor in heat resistance and light resistance depending on the kind of the dye or the polymer film. Moreover, there is a problem that the thickness of the film is relatively great.
In contrast, a method for forming a polarizing film by casting a liquid-crystalline coating fluid containing a lyotropic liquid crystal compound onto a substrate, such as a glass plate or a polymer film and the like to orient the lyotropic liquid crystal compound is known (JP 2006-323377 A). The lyotropic liquid crystal compound forms supramolecular aggregates exhibiting liquid crystallinity in the solution, so that the long axis direction of the supramolecular aggregates is oriented in a flowing direction when flowing after applying shearing stress onto the liquid-crystalline coating fluid containing this. Lyotropic liquid crystal compounds-based polarizing films do not need to be stretched and are easy to have a wider width because of no shrinkage in a width direction by stretching. Further, the lyotropic liquid crystal compounds-based polarizing films are expected to have potential because the thickness can be reduced significantly.
However, the polarizing film obtained by casting a conventional liquid-crystalline coating fluid has a drawback that fine crystals of some ten μm are separated out in the film in a drying process, resulting in an increase in haze value of the polarizing film. Moreover, the orientation degree of the lyotropic liquid crystal compounds becomes lower, so that the dichroic ratio becomes smaller, which has become a problem. Thus, a liquid-crystalline coating fluid which has resolved this problem has been demanded.
It is an object of the present invention in a polarizing film obtained from a liquid-crystalline coating fluid containing a lyotropic liquid crystal compound to provide a liquid-crystalline coating fluid which has resolved the drawbacks of the polarizing film caused by a reduction of dichroic ratio because of an increase in haze value of the polarizing film by the separating of fine crystals in the film and the lowered orientation degree.